With respect to feeding parts, a part-feeding method of the taping system has proven to have high reliability in mounting (or packaging) electronic parts and have been widely used recently, providing a main method for supplying parts. In this part-feeding method, parts, packaged in part carriers connected into a tape form, are charged into an automatic feeder in the packaged state and automatically fed one by one. However, in the part-feeding of the taping system, since part-carrier tapes, such as paper tapes and embossed tapes, constituting the part-packaging containers are disposed after their use, it has been pointed out that they cause large amounts of industrial wastes with an increase of the use of parts. To solve this problem, part-carrier tapes which are capable of being re-used have been proposed as disclosed in Japanese Laid-Open Patent Publication 156562/1994 (Tokukaihei 6-156562).
With respect to resin materials for the part-carrier tapes, in the case of the application to general mechanism assembling parts, a polypropylene resin has been used because of its advantages in mechanical properties (rigidity, hinge strength), heat resistance, moldability, re-usability, recycling property (re-moldability after size reduction) and costs.
In the case of the application to housing containers for electronic parts, electric conductivity is particularly required so as to prevent electrostatic breakdown in electronic parts; however, when carbon is added to the conventional polypropylene resin so as to impart electric conductivity, its mechanical strength is extremely reduced with the result that it cannot be put into practical use. Therefore, conventionally, a conductive polystyrene resin to which carbon is added has been applied. Here, the hinge strength is defined by the number of repeated bending operations which are carried out by a hinge tester until separation under the condition of right-to-left bending angles of 45 degrees, a load of 800 g and a bending speed of 60 times per minute, and the hinge strength required for sufficient recycling property is regarded as not less than 100 times.
However, in the case of housing, in particular, semiconductor packages as packaging containers for electronic parts, the following problems are encountered. At present, since not less than 90% of the semiconductor packages are epoxy resin molded packages with high hygroscopicity, the packages tend to absorb water in the presence of moisture. If these moistened packages, as they are, are soldered in a reflow furnace, water contained inside the mold packages abruptly becomes water vapor, causing the packages to explode and to be damaged. Therefore, it is necessary to carry out a so-called baking process for heating and drying the packages at approximately 125° C. prior to assembling and mounting the packages. However, the above-mentioned conductive polystyrene resin is inferior in heat resistance, and can not resist baking at 120° C. or higher. Consequently, it is necessary to prepare counter-measures such as baking the electronic parts in a separate manner immediately before mounting (or packaging) them, or baking the electronic parts separately and then housing and sealing them into the container by applying top tapes, etc. thereto.
In recent years, there have been continual efforts to develop a conductive polypropylene resin which is superior in mechanical properties, has high heat resistance, reduces costs, and also does not emit toxic substances even when it is disposed or burnt. However, those materials that are made by adding carbon to a polypropylene resin having a low crystallinity so as to impart conductivity unfortunately have insufficient rigidity, and when they are used for the carrier tapes for the electronic parts, they provide an insufficient part-retaining force through a shutter portion for pressing the electronic parts, and the containers are susceptible to deformation due to external forces applied upon transportation; thus, it is not possible to put them into practical use due to low reliability in mounting. On the other hand, those materials made by adding carbon to a polypropylene having a high crystallinity have sufficient rigidity. However, they have insufficient hinge strength, and are subject to fatigue in the shutter portion due to repeated opening and closing processes, thereby providing a low re-usable property and failing to allow for practical use. As described above, those containers made from the conventional conductive propylene resin unfortunately provide insufficient rigidity or hinge strength although they have the heat resistance, thereby failing to provide sufficient reliability in mounting and re-using property.
Moreover, from the standpoint of efficiency, the above-mentioned part carrier tapes, etc. should be wound up onto a reel and baked as they are together with the packaged parts. However, most of the conventional reel materials, which are made from a paper material or a resin material as in the containers, can not be baked together with the parts. Only reels made of expensive aluminum can be baked together with the parts.